Fishing adapters of the type in question are used by workmen passing flexible electrical wire or cables through masonry, concrete or timber walls or through other solid or semi-solid structures/media. Fishing adapters are designed to help to reduce the time needed to install the wire or cables. Although such devices are known as fishing adapters, for the avoidance of doubt it should be understood that they are not generally used to randomly angle for items to hook onto. Instead the item to be pulled through the wall is deliberately placed on the hook when the hook projects through the wall.
By way of example, when installing cable from a satellite TV dish or TV aerial that is mounted to the outside of an external brick wall of a building it is necessary to pass the cable through a passageway that is drilled through the brick wall in order to reach the internal socket or to run the cable to the indoors receiver box or TV. A 300 mm or 400 mm long masonry drill bit or longer is required to penetrate fully through the thickness of most masonry walls and especially cavity walls and the drill bit should be of the type that is normally designed to vibrate as little as possible during hole creation, be as resistant as possible to snagging and be able to transport mortar or brick dust back out of the hole while remaining sharp while drilling into the brick or mortar. For the purposes of the present invention, however, the vibration-damping qualities of the drill bit are not particularly relevant. When the drill bit is being withdrawn, even if rotating under power and with hammer action selected, there is generally no vibration of the drill bit since the percussion hammer does not contact the drill bit.
Once the drill bit has penetrated to the far side of the wall, traditionally it would be withdrawn and a ‘fishing tape’ (or steel wire with a loop at the end) would be fed through the hole to the far side and the cable end attached to it to pull the cable on the fishing tape back through the hole. This is effective but inevitably somewhat time-consuming. More recently time-saving proposals have been made to modify the drill bit to have a notch to be able to hook the cable to the drill bit so that the cable can be pulled through the hole by the drill as the drill is retracted. This avoids the need to separately guide a ‘fishing tape’ through the hole first and can save valuable minutes of expensive work-man time. An example such modified drill bit arrangement is disclosed in UK Patent GB 23017888 and is useful but due to the location of the notch on the drill bit can weaken the drill bit tip and is also not fully secure and makes secure attachment of the cable difficult. A variant of the idea of using the drill bit itself as the fishing tool is, as exemplified in U.S. Pat. No. 4,033,703, to provide a fishing adapter that holds the cable end and mounts by a latch mechanism to the drill bit and thus couples the cable to the drill bit for pulling the cable through the hole.
Despite advances in masonry drill bit design and coatings, snagging can still be a significant problem and notably when seeking to retract the drill bit after the cable passage hole has been formed. When a rotating drill bit passes through certain materials, including porous materials such as soft brick and stone used in the construction of buildings, dust and hard particles of debris are created. This effect is amplified if a drill with a percussion facility is employed. This debris often binds in the flutes around the drill bit. Often it is necessary to run the drill in forward or reverse rotation in order to be able to release it from brick and mortar dust and debris in the passageway to be able to retract the drill. This is straightforward to do when the drill is being retracted on its own but not straightforward if the cable is coupled to the drill bit.
In the cases where the cable is hooked directly onto a modified drill bit or via an intermediate fishing adapter that is latched to the drill bit there is often no opportunity to run the drill since this will risk serious damage and entanglement of the cable. Thus with the existing modified drill bit arrangement and fishing adapter arrangement the workman has no option but to repeatedly insert and retract the running drill to clear all debris before seeking to attach the cable to the bit. The hoped for time-savings of the modified drill bit arrangement and fishing adapter arrangement are thus often lost in practice. Furthermore, for some types of walls and constructions such as those with loose rubble in-filled cavities any amount of preparative clearing of the hole/passageway before trying to couple the cable to the drill bit may be fruitless and necessitate the workman resorting to using the traditional fishing tape approach instead. Modern cavity walls filled with insulation material in the cavity can present a similar problem when trying to use the traditional fishing devices.
It is an object of the present invention to address these short-comings of the prior art in order to provide a fishing adapter arrangement that is practical for use in a wide range of situations, including rubble in-filled walls and similar, and which avoids the need for preparative clearing of the hole/passageway.